<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script src="./js/vue.js"></script>
    <div id='app'>
        <div v-if="isShow" ref="self">test</div>
        <button @click="isShow=!isShow">更新</button>
    </div>

    <script>
        let app = new Vue({
            el: "#app",
            data: {
                isShow: false
            },
            beforeUpdate() {//vue实例挂载完成后，数据发生变化，会执行beforeUpdate和updated钩子函数
                console.log('更新之前');
                console.log(this.$refs.self);//打印出数据更新之前的内容
            },
            updated() {
                console.log("更新之后");
                console.log(this.$refs.self);//打印出数据更新之后的内容
            }
        })
    </script>
</body>

</html>